HK1166165B - Annular light guide illuminator and optical scanner - Google Patents

Description

Annular light guide illuminator and optical scanner

Technical Field

The present invention relates to the technical field of optical devices for illuminating an area to be imaged and corresponding imaging devices. In particular, the present invention relates to imaging devices, such as optical scanners, used to scan an area on an article in order to detect/read some indicia located on the article.

Background

Imaging devices are commonly used to scan a mark on an article, such as optical scanners as illustrated in the U.S. patents US6,352,204B2, US 7,357,326B2, US 7,370,801B2, and US 7,419,098B 2. Such indicia may be a bar code (a linear or data matrix-like two-dimensional bar code) or may be any other pattern that includes authentication data corresponding to an item. In some cases, a mark on the surface of an item is invisible or difficult to see with the naked eye (e.g., a design printed in phosphorescent, luminescent, or fluorescent ink) and/or may only be detectable under illumination with specific light (e.g., light in the UV or IR regions of the spectrum). Furthermore, even if the mark can be detected with visible light, its size may be so small or it may contain minute details of a small scale that it is still difficult to read, thus requiring good lighting conditions. Conventional scanner light sources (depending on which part of the spectrum is used to detect the mark) are incandescent bulbs (typically used at wavelengths between about 400nm and 2500 nm), flash lamps (e.g., similar to xenon high-pressure flash lamps), lasers or light emitting diodes (LEDs, emitting in the UV, visible or IR region, typically using wavelengths between about 250nm and 1 micron). The photodetectors traditionally used in scanners are CMOS (complementary metal oxide semiconductor) or CCD (charge coupled device) type cameras, photodiodes (single or multiple sets), phototransistor or photoresistor circuits, linear CMOS or CCD sensors.

Conventional optical scanners (which may be hand-held or stationary) include: a light source (which may include filters) for illuminating an area on the article with appropriate light; an illuminator (which may include focusing means) for appropriately delivering light received from the light source to the area; means for collecting light reflected from the area and transmitting it back to a light detector; a processing unit for analyzing the signal conveyed by this light detector (and detecting/reading or decoding data associated with a marker located within the region); and the control unit is used for controlling the illumination light source and the processing unit.

Conventional hand-held scanners (wired or cordless) generally further include a power module for powering the scanner, and may also include a radio module for wireless communication (e.g., via Wi-Fi), a display module (e.g., a LCD or crt display) for displaying measured data or scan parameters, and a control interface (including buttons with multiple functions and an ON/OFF switch button) for entering scan conditions. Conventional optical scanners may additionally incorporate an RFID (radio frequency identification) circuit so that RFID chips located on a scanned item may be read (see, for example, US6,264,106B 1), thus enabling the scanner to read a combined optical/RFID tag.

A typical problem with optical scanners is that: illuminating an area at a highly uniform and sufficiently intense level on a reflective surface of an article comprising a mark so that the detector of the scanner can read the mark from the reflected light, while minimizing stray light and avoiding "hot spots" on the illuminated surface that reduce contrast and can cause serious image processing problems; the detection of this marker may even fail if the image sensor is already saturated. In addition, the above problem is further increased if the reflecting surface is curved.

The above-cited prior art documents have taken this into account (see e.g. US6,352,204B2 column 1 lines 36 to 51; US 7,357,326B2 column 2 lines 16 to 19; US 7,370,801B2 column 2 lines 6 to 17; and US 7,419,098B2 column 2 lines 1 to 11) and have proposed some specific lighting techniques.

Document US6,352,204B2 discloses that an area on an article is illuminated at a low angle of incidence so that a "wash out effect" due to shiny or irregular surfaces can be minimized. However, a problem remains with respect to stray light.

Documents US 7,357,326B2, US 7,370,801B2 and US 7,419,098B2 disclose the use of an illuminator having a nose piece in the shape of a truncated pyramid, which directly illuminates an area on the article by placing the converging end of the nose piece near the area, so that light from the light source reaches only a predetermined area, while being shielded from too much ambient light. The opposite, diverging end of the nosepiece receives light from the light source. However, some problems remain as follows: light rays (returning to the light detector) are reflected directly at the inner surface of the nosepiece (even though this surface may be an uneven reflective surface with irregularities so as to scatter the light rays), and "spots" may also be formed on the reflective surface of the article.

Disclosure of Invention

It is an object of the present invention to provide a lighting technique which avoids the disadvantages of the prior art.

The present invention relates to an optical scanner, and more particularly to a hand-held optical scanner for detecting and reading a mark located at the surface of an object, and which implements the illumination technique.

According to one aspect of the present invention, an annular light guide illuminator is operable to guide light received at an inlet surface to an outlet surface so as to illuminate a region at a distal end of the light guide illuminator, and to transmit light reflected/emitted from the region through an inner hole portion of the light guide illuminator,

wherein:

the outlet surface is a boundary surface portion of a frustoconical inner chamber, a bottom of the inner chamber leading to the distal end, and a truncated top end of the inner chamber opposite the bottom leading to the inner bore portion; and

the exit surface is operable to refract light received from the entrance surface so as to illuminate the area with a substantially uniform light intensity distribution.

With this annular structure of the illuminator, light from the light source is guided within the annular light guide so as not to pass through the inner hollow of the light guide, and the exit surface of the light guide forms the boundary of an inner chamber that tapers from adjacent its base (which is to be placed adjacent the area to be illuminated) to its truncated top end, thereby forming a bottleneck-like inner bore portion for transmitting light reflected from the area back. This configuration has the advantage of eliminating light directly from the exit surface from traveling back through the inner bore. Therefore, stray light due to internal reflection can be eliminated. In addition, when the distal end of the illuminator is positioned near (or in contact with) the target area to be illuminated, this constitutes a nosepiece that eliminates a significant amount of stray light from external sources. In addition, the shape of the exit surface is selected to make the light refracted to the bottom of the interior chamber sufficiently uniform to avoid the formation of a light spot on the illuminated surface near or in intimate contact with the bottom. All these features contribute to improving the detection of a mark by a scanner equipped with such an illuminator, since the contrast of the mark is strongly increased by the uniform illumination.

The illuminator of the present invention may also be used to transmit light emitted by a marker located in the target area through its interior aperture (e.g., in response to an excitation light transmitted through the exit surface in the case of fluorescent or phosphorescent markers).

The most useful shape of the exit surface portion can be simply estimated by the principle of refraction (Snell principle) and the height and bottom area of the inner chamber. However, a simple shape like a plane will generally be sufficient to provide good lighting conditions (e.g. in the case of an inner chamber like a truncated pyramid, since the various portions of the inner chamber surface correspond to the various surfaces of the truncated pyramid). Another example of a simple shape that can provide good lighting conditions is an exit surface that resembles a conical frustum (which corresponds to a straight generatrix). Better uniformity can be obtained by the shape of the outlet surface corresponding to a convex arc generatrix (the concavity of this arc is oriented towards the inner chamber). A still better degree of uniformity can be obtained if the generatrix is a parabola. In addition, even if the broad bottom end of the interior chamber opens into the area for illumination at the distal end of the light guide, the overall external shape of the illuminator forming a nosepiece can converge toward the distal end, thus concentrating the illumination on the target area to enhance the readability of a mark located within the area.

The annular light guide illuminator according to the present invention may be designed to direct light corresponding to electromagnetic radiation included in the UV to IR optical range (i.e., about 400nm to about 2500nm wavelength). As is well known to those skilled in the art, the material from which the light guide is constructed must be selected precisely in accordance with the light to be guided. The illuminator may also be designed to direct electromagnetic waves having different wavelengths.

Although the annular light guide of the present invention can be made hollow, i.e., having only inner and outer peripheral material faces for guiding light by reflection and a material exit face (and possibly a material entrance face) for illuminating the inner chamber by refracting some of the guided light, a preferred embodiment of the present invention corresponds to a solid annular light guide illuminator made of substantially transparent material. Such materials are selected so that the light to be guided is substantially transparent. The substantially transparent material of the solid body may be selected from the group consisting of glass, glass-ceramic materials, crystalline materials, and plastic materials. The crystalline material is preferably selected from quartz, yttrium-aluminum garnet (yttrium-aluminum garnet), and sapphire (sapphire). The optical plastic material is preferably selected from the group consisting of polymethylpentene (TPX), Polymethylmethacrylate (PMMA), methylmethacrylate/styrene copolymer (NAS), styrene-acrylonitrile (SAN), Polycarbonate (PC), and Polystyrene (PS).

In order to avoid stray light radiation (e.g. for protecting an operator from radiation), the annular light guide luminaire according to the invention additionally comprises a cover made of a material that is opaque to the guided light on a portion of its peripheral surface. In order to avoid stray light originating from the inner peripheral surface of the inner hole portion of the light guide, the illuminator according to the present invention further includes a cover made of a material opaque to guided light on a part of its inner peripheral surface, in its inner hole portion. For example, the cover may be a cover or a coating (coating).

The annular light guide illuminator according to the present invention may further comprise an RF antenna mounted on a portion of its peripheral boundary surface, adapted to receive an RFID signal from an RFID chip located at the level of the area, and also adapted to transmit this RFID signal to the RFID chip. Such an embodiment of the illuminator according to the present invention, when used in a scanner, will read optical symbols and RF data presented on a target area.

The annular light guide luminaire according to the invention is compatible with a conventional diffusive insert for scattering light, which is arranged, for example, at the level of the inlet face. However, in a preferred embodiment, the annular light guide illuminator has a portion of the exit surface or a portion of the entrance surface roughened to scatter light traveling toward the target area. This scattering improves the uniformity of the light at the target area and can be achieved by conventional techniques (like surface sanding) or by forming many regular or irregular uneven defects/patterns on the surface (acting as scattering centers). The luminaire according to the invention therefore does not rely on a diffusive insert between the light source and the luminaire and can therefore be made more compact.

The annular light guide illuminator according to the present invention may also be adapted to receive an optical device to collect and transmit light reflected from the illuminated area and transmitted through the inner bore. For example, the hollow portion of the annular light guide above the inner chamber (i.e., between the entrance portion of the light guide and the inner bore portion near the converging end of the inner chamber) may be provided with means for mounting the optical device. For example, the mounting means may comprise any groove, notch, protrusion or thread on the inner peripheral surface of the light guide (above the inner chamber), or any other fastening means (e.g. using glue, screws, or inserted brackets).

As mentioned before, the luminaire according to the invention has a number of advantages. Furthermore, the illuminator may have a variety of overall shapes when light is directed within the annular light guide, and the illuminator may thus be readily adapted to deliver illumination between specific light source configurations and a target area, while minimizing light loss and still having substantially uniform illumination conditions within the area. As a result, it is no longer necessary to precisely position the distal end of the illuminator over the target area to be scanned in order to have a substantially uniform illumination. In addition, the distal end of the illuminator may also be shaped to be more easily positioned in front of a target area, which is particularly useful when the illuminator is mounted on a handheld scanner. For example, the distal end may be slightly tilted without compromising the uniformity of illumination over the target area.

This ring-like configuration also allows the use of many types of light sources, such as incandescent bulbs, discharge tubes, flash lamps, lasers or light emitting diodes (from UV to IR), or combinations of these light sources, in order to illuminate the entrance surface. Since this entry surface can conform to the light source, for example, the use of Light Emitting Diodes (LEDs) equipped with lenses is no longer necessary: conventional LEDs with a wide emission angle may be used instead. Likewise, filters can also be easily configured at the entrance surface and/or the exit surface.

Likewise, the hollow interior of the light guide can be readily adapted to convey reflected light to many types of light detectors, such as those of the CMOS (complementary metal oxide semiconductor) or CCD (charge coupled device) type cameras, photodiodes (single or multiple sets), phototransistor or photoresistor circuits, linear CMOS or CCD sensors.

Another aspect of the present invention relates to an optical scanner, comprising:

an annular light guide illuminator according to the previous aspect of the invention, adapted to receive an optical device, as described above, to collect and transmit light reflected from the illuminated area and transmitted through the inner bore;

a light source operable to illuminate the entrance surface of the light guide illuminator; and

a light detector operable to receive light transmitted by the optical device.

The optical scanner may include the above-described annular light guide illuminator with an optional RF antenna, and may additionally include:

an RF control circuit for transmitting an RFID signal to an RFID chip located at the zone level via the RF antenna; and

an RFID reader operable to read an RFID signal received from the RFID chip.

The optical scanner implemented according to the present invention may be a handheld scanner including a power module for supplying power to the scanner, and may further include at least one of a wireless communication module, a display module for displaying measured data or scanning parameters, and a control interface for inputting scanning conditions. The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which like reference numerals refer to like elements throughout the different views, and in which various salient aspects and features of the invention are illustrated.

Drawings

Fig. 1A-1C show cross-sectional views of an annular light guide illuminator implemented in accordance with the present invention.

FIG. 1D illustrates a partially cut-away perspective view of the annular light guide illuminator of FIG. 1A or 1B.

Fig. 2A-2D show some perspective views of ring light guide illuminators with different shapes implemented according to the present invention.

Fig. 3A-3D show views of an annular light guide illuminator with multiple scattering surfaces implemented in accordance with the present invention.

Fig. 4A shows an exploded perspective view of a portion of a luminaire implemented according to an embodiment of the present invention, including an RFID antenna.

Fig. 4B shows a perspective view of the illuminator in fig. 4A.

FIG. 4C shows a cross-sectional view of a variation of the annular light guide illuminator of FIG. 4B.

Fig. 5 illustrates a perspective view of a handheld scanner implemented in accordance with an embodiment of the present invention.

Fig. 6 shows an exploded perspective view of a portion of the handheld scanner of fig. 5.

FIG. 7 shows a cross-sectional view of a variation of an annular light guide illuminator implemented in accordance with the present invention.

Detailed Description

The principle of an illuminator implemented in accordance with the present invention is illustrated in FIG. 1A, which shows a cross-sectional view of an annular light guide illuminator 10, with a plurality of light sources 11 illuminating the entrance surface 12 of the light guide illuminator 10. Light is guided within the guide portion 13 of the light guide illuminator 10 by reflection between an inner peripheral surface 14 and an outer peripheral surface 15 to an exit surface 16, which refracts the light to a target area 17 at the surface of an article (not shown). The outlet surface 16 constitutes a boundary surface of a frustoconical inner chamber 18, preferably convexly curved, while the inner chamber 18 has a diverging bottom end 19 leading to the target area 17 and a truncated top end 20 leading to an inner bore portion 21 of the light-guiding illuminator (i.e. a converging end opposite the bottom end).

FIG. 1D shows a partially cut-away perspective view of the ring light guide illuminator 10 with a transparent solid guide 13.

FIG. 1B shows a cross-sectional view of an illuminator 10, equipped with: a plurality of light sources 11 arranged around the entrance surface 12; and a light detector 30 for detecting light that is diffused (reflected) back from the target area 17 on a surface 25 of an article and transmitted through the inner chamber 18 and the inner hole portion 21. In this example, the light detector 30 is mounted on the same support 31 as the light sources 11 above the entrance surface of the illuminator. The inner peripheral boundary surface 14 of the annular light guide illuminator 10 has a plurality of protrusions for easily mounting an optical device 32 within the inner hollow 21, and this optical device 32 is used in this case to focus light to the light detector 30.

Fig. 1C shows a cross-sectional view of an illuminator 10 provided with a housing 40, 41, which in this example is a hollow housing (or cover) made of opaque material and arranged around the inner and outer peripheral surfaces 14, 15 of the annular light guide illuminator. The outer part 40 of the cover covers the peripheral surface 15 and the inner part 41 of the cover covers the inner peripheral surface 14, and therefore there is no stray light in the guide 13 of the luminaire, which is neither deflected to the outside nor to the inner hole of the light-guiding luminaire. The structure of the housing protects the operator's eyes from light escaping through the outer guide surface 15 and also protects the light detector (see fig. 1B) or other optical devices from stray light transmitted directly through the inner guide surface 14. The cover may also be a coating applied to the guide surfaces of the light guide illuminator (e.g., a layer of metal formed on the surfaces or an opaque composition coating applied thereto).

The overall cross-sectional shape of the annular light guide illuminator according to the present invention is not limited to a truncated square pyramid (see fig. 2D), but may be any shape whose topology is annular. Likewise, the shape of the inner aperture portion may be arbitrary, but it is only necessary that reflected light from the target area (or light emitted by a target surface located on the article) be transmitted to a light detector. If mirrors are used to direct the light received by the inner chamber 18 to, for example, a light detector, the ring shape may even be curved at the height of the inner bore portion 21. Illustrative and non-limiting examples of some shapes (global shape, internal chamber shape, internal bore shape) are shown in fig. 2A-2C.

In one embodiment of the invention, as shown in fig. 3A, the entrance surface 12 of the light guide illuminator is sanded to better diffuse light (by scattering of light due to surface roughness) within the guide portion 13. The outlet surface may also be sanded to diffuse light within the interior chamber 18. Scattering has a "smoothing" effect and thus can help avoid the formation of bright "hot" spots on the target surface of the article. This is illustrated in fig. 3B, which shows a cross-sectional view of a luminaire having a sanded exit surface 15. Light scattering may also be enhanced by a plurality of (regular or irregular) ridges formed on the exit surface, for example, as shown in fig. 3C and 3D.

In the embodiment shown in fig. 3A to 3D, the guide 13 is a solid PMMA (polymethyl methacrylate) body for guiding ultraviolet light having a wavelength generally between 300nm and 450 nm.

In embodiments of the invention, the luminaire is adapted to additionally house an RFID (radio frequency identification) antenna. This is illustrated in fig. 4A and 4B, where an antenna 43 is wound around the peripheral surface of a cover 40 disposed over the peripheral surface 15 of the annular light guide illuminator 10 and connected to an RFID (radio frequency identification) circuit 42. However, this RFID antenna may be configured on other components of the luminaire. As an example, FIG. 4C shows an RFID antenna 43 wrapped within the inner bore portion 21 of the annular lightguide illuminator and wrapped around an optical device 32, the optical device 32 being used to focus light received through the truncated top end of the inner chamber 18 onto the light detector 30 mounted on the support 31. As also shown in fig. 4C, a light source, which is an LED bar 33, is mounted on the support 31 so as to directly face the entrance surface of the annular light guide illuminator. The RFID antenna may also have other shapes (not necessarily a wound wire, but rather depending on the RF signal to be transmitted/received), as is well known in the art.

Fig. 5 shows a perspective view of a handheld optical scanner 50 implemented in accordance with the present invention. The scanner includes: an annular light guide illuminator 10 for illuminating a portion of the surface 25 of an article (here a can); a housing having a handle 51 which can be easily held by an operator; a power module 52 for providing power to the scanner; and a display 53 (liquid crystal display LCD) having a touch screen so as to omit many keys (a keyboard is displayed ON the LCD) except for ON/OFF/Reset (ON/OFF/Reset) keys (not shown). Fig. 6 is an exploded view of a portion of a hand-held scanner 50 including an illuminator 10 provided with a cover 40 and an optical device 32, the optical device 32 being mounted on a support 31 (optical detector not shown) along with a plurality of light sources 11. This cordless optical scanner 50 is balanced for easier handling and comprises the following components:

an optical integrated body, comprising: a light source 11 (with a plurality of LEDs); an annular light guide illuminator 10 equipped with a cover 40 for illuminating a bar code or data matrix on an object 25; and a CCD (charge coupled device) camera mounted on the support 31;

an LCD color touch screen 53;

a main board (not shown) on which a CPU (central processing unit) is disposed for reading/decoding the bar code or matrix code and controlling the scanner;

a wireless communication board (GSM/GPRS);

a battery pack 52; and

ergonomic housing (plastic).

Many variations of the above-described hand-held scanner have been implemented: which may be autonomous in the process of reading/verifying or authenticating a tag, or may be connected to a station having the processing capabilities described above (if verification or authentication of the item is performed, for example, by comparison with data in an external database), the connection to the station may be wired (e.g., via ethernet or telephone modem) or wireless (e.g., via Wi-Fi, GSM/GPRS or bluetooth). Even with autonomous processing capabilities, the handheld scanner may still include communication capabilities. The hand-held scanner may also be equipped with a connection device (e.g., to be connected to a storage device (docking) station) for charging the battery of its power module. In a preferred embodiment, the hand-held scanner is balanced and the end of its nosepiece can be further tilted so that the operator can easily scan an item in any position (e.g., standing, squatting, or kneeling).

The present invention is not limited to the embodiments described above, and various modifications can be made without departing from the scope of the present invention as defined in the claims. For example, the shape of the illuminator may be altered (as shown, for example, in fig. 7 with side entry surfaces 12). Likewise, the above-described (handheld) scanner may include an illuminator implemented according to any of its variations, and/or may be adapted to use other portions of this spectrum, still in the UV-IR range, in order to illuminate a target area, or to detect light being reflected/emitted from this area.

Claims (17)

1. An annular light guide illuminator operable to guide light received at an entrance surface to an exit surface to illuminate an area at a distal end of the light guide illuminator and to transmit light reflected/emitted from the area through an inner hole portion of the light guide illuminator,

wherein:

said outlet surface is a boundary surface portion of a frustoconical inner chamber with a bottom end of said inner chamber opening into said distal end and a truncated top end of said inner chamber disposed opposite said bottom end opening into said inner bore portion;

the concave surface of the arcuate generatrix of a portion of the outlet surface is oriented toward the inner chamber; and

the exit surface is operable to refract light received from the entrance surface to illuminate the area with a substantially uniform light intensity distribution.

2. The annular light guide illuminator of claim 1, wherein the bus bar is a parabola.

3. The annular light guide illuminator of claim 1 or 2, operable to guide light rays corresponding to electromagnetic radiation comprising a UV to IR wavelength range.

4. The annular light guide illuminator of claim 1, wherein the annular light guide illuminator is a solid body made of a substantially transparent material.

5. The annular light guide illuminator of claim 4, wherein the substantially transparent material is selected from the group consisting of glass, glass-ceramic materials, crystalline materials, and plastic materials.

6. The annular light guide illuminator of claim 5, wherein the crystalline material is selected from the group consisting of quartz, yttrium aluminum garnet, and sapphire.

7. The annular light guide illuminator of claim 5, wherein the plastic material is selected from the group consisting of polymethylpentene (TPX), Polymethylmethacrylate (PMMA), methylmethacrylate/styrene copolymer (NAS), styrene-acrylonitrile (SAN), Polycarbonate (PC), and Polystyrene (PS).

8. The annular light guide illuminator of claim 1, wherein a portion of the exit surface or the entrance surface is roughened to scatter light.

9. The annular light guide illuminator of claim 1, further comprising a shield made of a material opaque to guided light on a portion of an outer peripheral surface of the light guide illuminator.

10. The annular light guide illuminator of claim 1, further comprising a shield made of a material opaque to guided light in the inner bore of the light guide illuminator over a portion of an inner peripheral surface of the light guide illuminator.

11. The annular light guide illuminator of claim 1, wherein the entrance surface is planar.

12. The annular light guide illuminator of claim 1, further comprising an RF antenna mounted on a portion of its peripheral boundary surface adapted to receive RFID signals from an RFID chip located in the area and also adapted to transmit the RFID signals to the RFID chip.

13. The annular light guide illuminator of claim 1, further adapted to receive an optical device to collect and transmit light reflected/emitted by the illuminated area and transmitted through the inner bore portion.

14. An optical scanner comprising:

an annular light guide illuminator as defined in claim 13;

a light source operable to illuminate an entrance surface of the light guide illuminator; and

a light detector operable to receive light transmitted by the optical device.

15. The optical scanner according to claim 14, wherein the annular light guide illuminator is an annular light guide illuminator as defined in claim 12 and claim 13 when dependent on claim 12, the optical scanner further comprising:

an RF control circuit for transmitting an RFID signal via the RF antenna to an RFID chip located in the area; and

an RFID reader operable to read an RFID signal received from the RFID chip.

16. The optical scanner of claim 14 or 15, wherein said scanner is a hand-held scanner comprising a power module for supplying power to said scanner.

17. The optical scanner of claim 16, further comprising at least one of a wireless communication module, a display module for displaying measured data or scanning parameters, and a control interface for inputting scanning conditions.